Strange that when he has wind and sea movement he can’t come up with any other power supply than solar panels.
If it hits a patch where the breeze is exceptionally light and/or the seas are very smooth, anything but solar would be useless, and yet since the craft is so small he could still be able to be underway.
Plus, the other methods would interfere with the operation of the boat in one way or another.
Solar panels are perfect for this app.